Herpes simplex virus type 2 (HSV-2) is a pathogenic agent that is associated with serious public health problems including HIV-1 acquisition and over one million new cases of genital herpes per year in the US. Current methods to control HSV-2 including antiviral drugs, education, and barrier methods are inadequate, and the prevalence of HSV-2 infection is steadily increasing. The long-term goal of this proposal is to design an effective prophylactic HSV-2 vaccine. Several lines of evidence indicate the HSV-2-specific CD8 T-cell responses may be important in controlling the severity of HSV-2 infection. Little is known concerning the identity of the immunodominant HSV-2 antigens recognized by CD8 T-cells. Based upon the mechanisms of action of action of HSV-2-encoded immune evasion genes, and upon empiric data, we hypothesize that proteins in the viral tegument, which are injected into the cell during viral entry, and HSV-2 proteins that are synthesized shortly after infection, are the immunodominant CD8 antigens of HSV-2. We will test this hypothesis using assays that measure CD8 T-cell responses to defined HSV-2 antigens and peptides. The expression of a skin-homing receptor by HSV-2-specific CD8 T-cells will be used to both purify CD8 CTL for a short interval to finish antigen discovery, and also to enrich polyclonal HSV-2-specific CTL for these assays. The primary readouts, ELISPOT, CTL, and tetramer assays, will be used to rank HSV-2 antigens in a hierarchy of immunodominance. To focus resources, analysis of subjects with asymptomatic HSV-2 infection, low HSV-2 shedding rates, and the prevalent HLA A*0201 allele will be emphasized. We further hypothesize that variations in CD8 T-cell responses to HSV-2 may be associated with disease HSV-2 severity. To test this hypothesis, we will characterize study subjects with HLA A*0201 and severe, symptomatic HSV-2 infection, and compare HSV-2-specific CD8 responses between persons with mild and severe infection. Assays will focus on responses to the HSV-2 antigens found to be immunodominant in HLA A*0201-bearing persons with asymptomatic infection. If our hypotheses is correct, we will have identified HSV-2 antigens that are rational components of a future generation HSV-2 vaccine, and will have a strong rational with development of a prophylactic or therapeutic vaccination format that will be elicit HSV-2-specific CD8 responses.